flow serve pump q=100m3/h & head 50m but delivering only 35m3/h 1

[jithin john]

good evening friends ,

recently installed a new flow serve pump with flow=100m3/h and head 50m and is delivering only 35m3/h.please explain the possible reasons were we have gone wrong .

Thank you all

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[LittleInch]

The difference between 35 an 100 m3/hr is a differential head of 55m to 50m.

That's not a lot.

Also unless you get your actual pump tested the basic parameters can change between "identical" pumps by 5 to 10% at this sort of size.

So impellor might be a little smaller than it should be, or your resistance is higher.

Also make sure it is going round the right way. A 3 phase supply is easy to get it wrong.

How much power is it taking?

Ate these pumps in parallel?

How are you measuring flow?

Do you have any idea what your system curve looks like?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

Is this a replacement pump?

Have you checked the head loss in the piping?

What is the discharge pressure?

Remember that pumps don't create pressure, pumps create flow. The discharge pressure is created by the piping.

 

[TugboatEng]

That is true for positive displacement pumps but centrifugal pumps create pressure in the volute or diffuser.

 

[Compositepro]

The impeller in a centrifugal pump applies forces to a fluid to get it moving. This will, of course, result in pressure gradients in the fluid on a microscopic basis. The piston of a positive displacement pump does exactly the same thing. The volute directs this motion in one direction, which again will result is microscopic pressure gradients, but no pressure in the fluid at the exit of the pump. In a centrifugal pump pressure can only be generated by converting momentum (fluid motion) to pressure. A piston pump cannot generate pressure without moving the piston (causing flow).

So there is no real difference between the two types of pump when it comes to the flow vs pressure concept. Pressure is created by a resistance to flow.

 

[EdStainless]

Check the speed also (a few RPM can matter) when you look at the actual dP across the pump.
What is your fluid? At what temp? After all the curves are based on cold water.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[jithin john]

Thankyou everyone for your replies

this is a replacement pump .There were 2 sets of KSB pumps with head 50m and 35m3/h flow for one pump. But the actual flow was around 24m3/h. So decided to replace with flow serve pump @50M and 100m3/h .

pump sets are in parallel
measuring flow using Siemens flow sensor + transmitter
Discharge pressure of flow serve pump is 5.9 bar
Suction pressure = 0.15 bar

piping -it a DN 100 DI pipe line for about 3.6 km with about 7-8 elbows .yesterday we found a dn 100 prv on the pipeline (still figuring why it is placed on a pumping line )
We also opened one washout before the prv and found pump delivering at 90m3/h

Fluid -pure water with pH 7 to <8

thank you all .hope this info helps

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[LittleInch]

You need to match the pump to the system.

Just because the Duty point of a centrifugal pump is 100m3/hr at 50m doesn't mean that it will do that flow if the system resistance is different.

The control valve will be there for a reason. Find the reason. Might be pressure or flow or back pressure. Then size your pump to match the total system resistance. It's called design. [pre][/pre]

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

Further to above, your figures make sense.

Differential head is 5.9 - 0.15 = 5.75 bar so ~ 56m

From pump curve 56m is about 35 m3/hr.

You will get no where in this unless you know.

Elevation difference from one end to the other
Arrival head / pressure required
Length of pipeline
ID of pipeline
Pressure loss vs flow accross your control valve.

Then you can generate a system curve.
Find out from that what pressure is needed at the inlet to do your required flow.
Subtract the inlet pressure into the pump at that flow.

This will give you the correct differential head to go buy the right sized pump....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[itsmoked]

Thanks LI for that clear summation.

Keith Cress
kcress -

http://www.flaminsystems.com